Hybrid-electric and pure electric vehicles rely on a traction battery to provide power for propulsion. The traction battery typically includes a number of battery cells connected in various configurations. To ensure optimal operation of the vehicle, various properties of the traction battery may be monitored. One useful property is the battery state of charge (SOC), which indicates the amount of charge stored in the battery. The SOC may be calculated for the traction battery as a whole and for each of the cells. The SOC of the traction battery provides an indication of the charge remaining. The SOC for each individual cell provides information that is useful for balancing the SOC between the cells. In addition to the SOC, battery allowable charging and discharging power limits can be used to determine the range of battery operation and to prevent battery excessive operation.